This then brings us to the other side of Mischel’s work, which is about resistance to temptation, and how we can exercise self-control over the course of development. This was exemplified in his famous “marshmallow experiment,” which he conducted over four decades ago at Stanford University. The basis of the experiment was simple. It left a number of small children, between 3 and 5 years old, alone in a room with a marshmallow on the table. Mischel explained to the children that they could eat the marshmallow now, or wait until he came back and got two more marshmallows. If the child wanted another marshmallow, they rang a bell to indicate their choice.
The aim of the experiment was to monitor delay of gratification in children. Mischel predicted that those children who were able to wait for the second marshmallow during the experiment would, later — in their adult life — have stronger resistance to other temptations, and, most importantly: be able to manage their impulse control better than those individuals who ate the marshmallow immediately. “The marshmallow study was designed to see when the child decides that they want the two marshmallows, how long will they actually persist to do so, after they have made the choice?” says Mischel.
The results of the original tests were stored on file and used later to correlate with a number of follow-up experiments that would produce further findings. The first one, which took place in 1988, displayed that children who delayed gratification for longer periods were described as significantly more competent during their teenage years. The follow-up study done in 1990, showed that those who had more success in delaying gratification had higher SAT scores, a lower body mass index, a better sense of self worth, pursued their goals more effectively, and coped more successfully with frustration and stress.
In 2011, with the aid of technology, Mischel did the most comprehensive follow-up study to date. His book that explains how the results matched up to his original hypothesis is titled “The Marshmallow Test: Mastering Self-Control.” In this experiment, he checked back on the children he first tested, who were now in their forties, and set up an impulse control task to examine behavior and neural correlates of delay of gratification, using functional magnetic resonance imaging (fMRI). This is technology that measures brain activity by detecting associated changes in blood flow. The experiments involved developing two tasks to examine impulse control, one in the presence of neutral “cool” stimuli, and one containing compelling “hot” stimuli.
As marshmallows are no longer likely to be as tempting as they were when the test subjects were children, Mischel altered the nature of his experiment ever so slightly. Instead of marshmallows, he used the social cues of faces with emotional expressions: happy faces relative to neutral and fearful faces.
The experiment tested whether individuals who were less able to delay gratification as children and young adults — known as low delayers — would now show less impulse control as adults. Or put simply: would they be able to resist reacting to the presence of a number of smiley faces?
Mischel explains the results: “In 2011 we followed our initial experiments with a study published in the journal The Proceedings of the National Academy of Sciences, and found that there were distinctive differences in their brain patterns in the fMRI, when those same individuals were in their 40s. We found more activation in the appetitive areas of the brain — that are connected both with obesity and proneness to drug addiction — for those individuals, who as kids, had rung the bell earlier.”
So are these activations in the brain prewired? Can they be learned? Or do they arise from the environment a child grows up in? Mischel confirms, as do most scientists in the present age, that there is no clear-cut answer to this question.
In “The Marshmallow Test” he tells the reader: “The conclusion is inescapable. Who we are emerges from a tightly intertwined dance between our environment and our genes that simply can’t be reduced to either part alone. But the unraveling mysteries of DNA, from breaking the code to sequencing the entire human genome and mapping its regulatory elements, provide a molecular basis for which our ‘nurture’ interacts with our ‘nature’ to make us who we are.”
So yes, argues Mischel, personality traits are not innate, nor are they entirely stable. And yet, as his marshmallow experiment shows — with decades of research and results to back up his claims — there are, seemingly, stable traits that we inherit from early childhood, perhaps from our environment, perhaps not, that stay with us for most of our life, determining how we behave and control our impulses and desires.
After reading over Mischel’s books and engaging him in a long conversation about the complexities of the human condition, a common theme begins to emerge — that human behavior is not a simple equation, but full of contradictions and complications that sometimes remain stable, but other times do not. “This word ‘personality’ covers a lot of ground, from general comments like, ‘she certainly has a lot of personality,’ to a much more contextualized and careful analysis,” says Mischel.
In everyday language the term “personality” often loses its meaning. The study of personality psychology — which is constantly evolving with new data all the time — attempts to bypass these stereotypes, and properly analyze the complex and irrational ways that human beings behave. “We are constantly able to transform what we become, by what we do, what we eat, how we live, and in how our relationships play out and so forth,” says Mischel.
Alongside the cold, hard statistics there’s optimism to be had. The tightly intertwined dance between our genes and the world around us continues, always leaving us room for hope and new opportunities, to change ourselves into the person we want to be.